Bypass switch for in-line power steal

ABSTRACT

A power supply unit for use with thermostats or other like devices. The power supply unit may keep electromagnetic interference emissions and harmonics at a minimum. A unit may have enough power for triggering a switch at about a cross over point of a waveform of input power to the unit. Power for triggering may come from a storage source. Power for the storage source may be provided with power stealing which require switching transistors which can generate emissions. In-line thermostats using MOSFETS power steal may do the power steal during an ON state (triac, relay or silicon controlled rectifier activated). Gate signals to the transistors may be especially shaped to keep emissions from transistor switching at a minimum. All that may be needed, during an OFF state as a bypass, is a high voltage controllable switch. The need may be achieved using high voltage MOSFETS.

BACKGROUND

The present disclosure pertains to thermostats and particularly tovarious kinds of power supply arrangements for thermostats.

SUMMARY

The disclosure reveals a power supply unit for use with thermostats orother like devices. The power supply unit may keep electromagneticinterference emissions and harmonics at a minimum. A unit may haveenough power for triggering a switch at about a cross over point of awaveform of input power to the unit. Power for triggering may come froma storage source. Power for the storage source may be provided withpower stealing which require switching transistors which can generateemissions. In-line thermostats using MOSFETS power steal may do thepower steal during an ON state (triac, relay or silicon controlledrectifier activated). Gate signals to the transistors may be especiallyshaped to keep emissions from transistor switching at a minimum. Allthat may be needed, during an OFF state as a bypass, is a high voltagecontrollable switch. The need may be achieved using high voltageMOSFETS.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 a is a block diagram of a thermostat circuit;

FIG. 1 b is a diagram of a power supply unit having a layout dividedinto several areas incorporating an off state area, an always activearea and an on state area;

FIG. 2 a is a diagram of a positive bypass switch;

FIG. 2 b is a diagram of a positive protect circuit connected to thepositive bypass switch;

FIG. 3 a is a diagram of a negative bypass switch;

FIG. 3 b is a diagram of a negative protect circuit connected to thenegative bypass switch;

FIG. 4 is a diagram of a circuit showing power steal switching MOSFETs;

FIG. 5 is a diagram of a circuit showing a large capacity capacitor;

FIG. 6 is a diagram of a DC-DC converter or linear regulator circuit;

FIG. 7 is a diagram of a half wave zero crossing detect circuit;

FIG. 8 a and FIG. 8 b are diagrams of a MOSFET gate signal shapingcircuit;

FIG. 9 is a diagram of a MOSFET reverse wave protection circuit;

FIG. 10 is a diagram of an SCR gate triggering signal circuit;

FIG. 11 is a diagram of an SCR circuit; and

FIG. 12 is a diagram of a plug that may be used for various connectionsexternal to the power supply unit.

DESCRIPTION

The present system and approach may incorporate one or more processors,computers, controllers, user interfaces, wireless and/or wireconnections, and/or the like, in an implementation described and/orshown herein.

This description may provide one or more illustrative and specificexamples or ways of implementing the present system and approach. Theremay be numerous other examples or ways of implementing the system andapproach.

There may be a need for a new kind of bypass which is non-currentlimited, inexpensive, small space, power dissipation proportional tocurrent consumption, audible noise free and electromagnetic interferencecompliant.

Since in-line thermostats using MOSFETS (metal-oxide-semiconductorfield-effect transistors) power steal may already do the power stealduring the ON state (triac, relay or silicon controlled rectifier (SCR)activated). All that may be needed, during the OFF state as a bypass, isa high voltage controllable switch. This may be achieved using highvoltage MOSFETS.

The thermostats may relate to HVAC (heating, ventilation and airconditioning) systems.

Using the same synchronization as for a MOSFET power steal, one maysynchronize the MOSFET switch. For an energy hungry application, thepeak current through the switch can became very high since the powersteal is half wave only. So, a second switch with small modification tothe synchronization circuit may be added to make a full wave switch andreduce harmonics.

The present approach may be used with an in-line controller doing MOSFETpower steal like the line volt thermostat. It may allow a circuit to beuniversal for virtually all thermostats, and that has characteristicssuch as being non-current limited, inexpensive, situated in a smallspace, having power dissipation proportional to current consumption, andbeing audible noise free and electromagnetic interference compliant. Thepresent approach may use one or more switches in a power steal circuitfor an in-line thermostat

FIG. 1 a is a block diagram of a thermostat circuit 71 discussed herein.An AC (alternating current) line voltage may be provided by power supply72 on lines 73 and 74 to thermostat 71 and electric baseboard 75. Linevoltage on line 73 may go to a bypass switch 76 and triac, relay or SCR77. Circuit low voltage may go along line 78 to stealing circuit 79. Aconnection may go from triac, relay or SCR 77 to a MOSFETs power stealalong line 81. Lines 78 and 81 may be connected by a line 83. A loadvoltage may connect stealing circuit 79 and MOSFETs power steal alonglines 84 and 85 via line 86 to electric baseboard 75. Areas 91, 92 and93 indicate off state, always active and on state, respectively.

FIG. 1 b is a diagram of a power supply unit 11 having a layout dividedinto three areas incorporating an off state area 12, an always activearea 13 and an on state area 14.

A positive bypass switch 15 in area 12 may have an input from a line 16(2). Also in area 15 is a negative bypass switch 17. Line 16 may go tonegative bypass switch 17. An AGND line 21 may be an input to switch 17.

Power steal switching MOSFETs 18 in area 13 may have an input from aline 19 (1) and be connected to an AGND (ground) line 21. A line 22 maygo from negative bypass switch to power steal switching MOSFETs 18.

An energy storage 23 in area 13 may receive an input of Vrect (stolenenergy) on line 24 from positive bypass switch 15 and an RS1G input online 24 from power steal switching MOSFETs 18. An output Vrect on line24 may go from energy storage 23 to a DC-DC (direct current) converteror linear regulator 25 of area 13. An output Vcc (3Vdc) on a line 26 maygo outside of unit 11 to a processor and circuits 27. Vrect on line 24may go to a backlight circuit 28 outside of unit 11. Vrect on line 24may also go to negative bypass switch 17.

A half wave ZC (zero crossing) detect 31 in area 13 may have an inputconnected to line 16 and an input connected to Vrect on line 24. Detect31 may output a D latch positive signal on a line 32, a D latch negativesignal on a line 33, and a crossing signal on a line 34. The signals onlines 32, 33 and 34 may go to a MOSFET gate signal shaping circuit 35 inarea 13.

A MOSFET reverse wave protection circuit 36 in area 13 may have an inputof Vrect on line 24 and of line 19 (1) of AC in. A protect signal on aline 37 may go from protection circuit 36 to shaping circuit 35. A Vsyncsignal on a line 38 may go from shaping circuit 35 to positive bypassswitch 15 and to negative bypass switch 17. A Vg signal may be on a line39 and may go to power steal switching MOSFETs 18.

An SCR gate triggering signal circuit 41 of area 14 may have inputs ofVrect on line 24, line 16 (2) of AC in and a CPU (computer) drive signalon a line 42. Circuit 41 may provide a gate signal Vgm+ on a line 43 anda gate signal Vgm− on a line 44 to an SCR circuit 45 of area 14. Line 16(2) of AC in may be an input to SCR circuit 45. An AC out on a line 46may be provided by circuit 45.

FIG. 2 a is a diagram of positive bypass switch 15. Switch 15 may beconnected to a positive protect circuit 51 as shown in a diagram of FIG.2 b. A Vdp signal may go on a line 53 from switch 15 to circuit 51.

FIG. 3 a is a diagram of negative bypass switch 17. Switch 17 may beconnected to a negative protect circuit 52 as shown in a diagram of FIG.3 b. A Vdn signal may go on a line 58 from switch 17 to circuit 52. Anover current terminal in circuit 51 may be connected via a line 57 withan over current terminal in circuit 52.

FIG. 4 is a diagram of circuit 18 showing power steal switching MOSFETs61 and 62. FIG. 5 is a diagram of circuit 23 showing a large capacity(e.g., 820 microfarads) capacitor 63. FIG. 6 is a diagram of a DC-DCconverter or linear regulator circuit 25.

FIG. 7 is a diagram of a half wave zero crossing detect circuit 31. FIG.8 a and FIG. 8 b are diagrams of MOSFET gate signal shaping circuit 35.Lines 21, 24, 34, 37 and 65 connect the diagrams of FIGS. 8 a and 8 b toshow the whole circuit 35. FIG. 9 is a diagram of MOSFET reverse waveprotection circuit 36.

FIG. 10 is a diagram of SCR gate triggering signal circuit 41, whichprovides trigger signals Vgm+ and Vgm− on lines 43 and 44 to SCR circuit45 shown in a diagram of FIG. 11.

FIG. 12 is a diagram of a plug 66 that may be used for variousconnections external to unit 11.

To recap, an in-line thermostat power system may incorporate a bypassswitch, a power stealing circuit connected to the bypass switch, anenergy storage circuit connected to the power stealing circuit, an SCRinterface circuit connected to the energy storage circuit, and an SCRcircuit connected to the SCR interface circuit. The bypass switch may bea controllable switch for line voltage.

The line voltage controllable switch may incorporate a positive bypassswitch and a negative bypass switch. The positive bypass switch mayincorporate one or more line voltage MOSFETs. The negative bypass switchmay incorporate one or more line voltage MOSFETs.

The positive bypass switch may incorporate a positive protect circuit.The negative bypass switch may incorporate a negative protect circuit.

The system may further incorporate a half wave zero crossing detectioncircuit connected to the energy storage circuit, and a gate signalshaping circuit connected to the half wave zero crossing detectioncircuit, the bypass switch, and the power stealing circuit. The powerstealing circuit may incorporate one or more switching MOSFETs. The gatesignal shaping circuit may provide a gate signal that results in a softtransition of turning on and off of the one or more MOSFETs of the powerstealing circuit.

The SCR interface circuit may have a first input connected to an outputof the energy storage circuit, a second input connectable to a linevoltage, a third input connectable to a control signal source, and anoutput of gate signals. The SCR circuit may have a first input for gatesignals from the SCR interface circuit, a second input connectable to aline voltage, and an output of a controlled line voltage.

The system may further incorporate a thermostat having a temperaturesensor, a temperature setting adjuster, and a processor connected to thetemperature sensor and a temperature setting adjuster. The processor mayincorporate the control signal source that provides a signal to the SCRinterface circuit which in turn outputs the gate signals to the SCRcircuit, with a goal to bring a temperature indication from thetemperature sensor and a temperature setting of the temperature settingadjuster to a same value.

The system may further incorporate a heater having terminals connectedto a line voltage and an output of the SCR circuit. The temperaturesensor may be situated in a space that contains the heater. The gatesignals to the SCR may result in the output of the SCR circuit tocontrol heat from the heater to achieve the goal to bring thetemperature indication from the temperature sensor and the temperaturesetting of the temperature setting adjuster to a same value.

A thermostatic power supply mechanism may incorporate a first terminalfor connection of a power source; a bypass switch having an inputconnected to the first terminal; an SCR circuit having a firstconnection connected to the first terminal, an input for a controlsignal, and a second connection connectable to a load; a second terminalfor connection to a load; a stealing circuit having an input connectedto an output of the bypass switch, and an output connected to the secondterminal; and a power steal module having an input connected to theoutput of the SCR circuit and an output connected to the secondterminal.

The bypass switch may incorporate one or more MOSFETs that are switched.The power steal module may incorporate one or more MOSFETs that areswitched to steal power. The stealing circuit may have an energy storageunit. Stolen power may go to the energy storage.

The energy storage cell may incorporate one or more super capacitors.

The bypass switch may have circuitry that incorporates a positive bypassswitching MOSFET, and a negative bypass switching MOSFET.

The mechanism may further incorporate a MOSFET gate signal shaper thatprovides a gate signal to the power steal module that softens atransition of turning on or off of the one or more MOSFETs.

The mechanism may further incorporate an SCR control signal circuithaving an output that provides the control signal to the input of theSCR circuit. The control signal provided to the input of the SCR circuitmay result in making power available or not available at the secondconnection of the SCR circuit. The second connection of the SCR circuitmay be connected to the load. The load may be a heater.

A power supply unit for a thermostat and electric heater may incorporatea bypass switch circuit having an input connectable to a first linevoltage, a power steal device having an input connectable to an outputof the bypass switch circuit, an energy storage having an inputconnected to an output of the power steal device, an SCR gate signalcircuit having an input connected to an output of the energy storage,and an SCR circuit having an input from an output of the SCR gate signalcircuit and an input connectable to a second line voltage, and having anoutput for providing a controlled second line voltage. The bypass switchcircuit may have one or more MOSFET switches. Also, the power stealdevice may have one or more MOSFET switches.

The unit may further incorporate a linear regulator connected to theoutput of the energy storage.

The unit may further incorporate a zero crossing detector having aninput connectable to the second line voltage.

The unit may further incorporate a FET gate signal shaping circuithaving an input for receiving zero crossing information from the zerocrossing detector and having an output for providing a sync signal tothe bypass switch circuit.

The unit may further incorporate a reverse wave protection circuithaving an input connected to the first line voltage, a second inputconnected to the output of the energy storage, and having an output forproviding a protect signal to the FET gate signal shaping circuit.

U.S. patent application Ser. No. 13/868,754, filed Apr. 23, 2013, andentitled “Triac or Bypass Circuit and MOSFET Power Steal Combination”,is hereby incorporated by reference.

In the present specification, some of the matter may be of ahypothetical or prophetic nature although stated in another manner ortense.

Although the present system and/or approach has been described withrespect to at least one illustrative example, many variations andmodifications will become apparent to those skilled in the art uponreading the specification. It is therefore the intention that theappended claims be interpreted as broadly as possible in view of therelated art to include all such variations and modifications.

What is claimed is:
 1. An in-line thermostat power system comprising: abypass switch; a power stealing circuit connected to the bypass switch;an energy storage circuit connected to the power stealing circuit; anSCR interface circuit connected to the energy storage circuit; and anSCR circuit connected to the SCR interface circuit; and wherein thebypass switch is a controllable switch for line voltage.
 2. The systemof claim 1, wherein: the line voltage controllable switch comprises apositive bypass switch and a negative bypass switch; the positive bypassswitch comprises one or more line voltage MOSFETs; and the negativebypass switch comprises one or more line voltage MOSFETs.
 3. The systemof claim 2, wherein: the positive bypass switch comprises a positiveprotect circuit; and the negative bypass switch comprises a negativeprotect circuit.
 4. The system of claim 2, further comprising: a halfwave zero crossing detection circuit connected to the energy storagecircuit; and a gate signal shaping circuit connected to the half wavezero crossing detection circuit, the bypass switch, and the powerstealing circuit; and wherein: the power stealing circuit comprises oneor more switching MOSFETs; and the gate signal shaping circuit providesa gate signal that results in a soft transition of turning on and off ofthe one or more MOSFETs of the power stealing circuit.
 5. The system ofclaim 1, wherein: the SCR interface circuit has a first input connectedto an output of the energy storage circuit, a second input connectableto a line voltage, a third input connectable to a control signal source,and an output of gate signals; and the SCR circuit has a first input forgate signals from the SCR interface circuit, a second input connectableto a line voltage, and an output of a controlled line voltage.
 6. Thesystem of claim 5, further comprising: a thermostat comprising: atemperature sensor; a temperature setting adjuster; and a processorconnected to the temperature sensor and a temperature setting adjuster;and wherein the processor comprises the control signal source thatprovides a signal to the SCR interface circuit which in turn outputs thegate signals to the SCR circuit, with a goal to bring a temperatureindication from the temperature sensor and a temperature setting of thetemperature setting adjuster to a same value.
 7. The system of claim 5,further comprising: a heater having terminals connected to a linevoltage and an output of the SCR circuit; and wherein: the temperaturesensor is situated in a space that contains the heater; and the gatesignals to the SCR result in the output of the SCR circuit to controlheat from the heater to achieve the goal to bring the temperatureindication from the temperature sensor and the temperature setting ofthe temperature setting adjuster to a same value.
 8. A thermostaticpower supply mechanism comprising: a first terminal for connection of apower source; a bypass switch having an input connected to the firstterminal; an SCR circuit having a first connection connected to thefirst terminal, an input for a control signal, and a second connectionconnectable to a load; a second terminal for connection to a load; astealing circuit having an input connected to an output of the bypassswitch, and an output connected to the second terminal; and a powersteal module having an input connected to the output of the SCR circuitand an output connected to the second terminal.
 9. The mechanism ofclaim 8, wherein: the bypass switch comprises one or more MOSFETs thatare switched; the power steal module comprises one or more MOSFETs thatare switched to steal power; the stealing circuit comprises an energystorage unit; and stolen power goes to the energy storage.
 10. Themechanism of claim 8, wherein the energy storage cell comprises one ormore super capacitors.
 11. The mechanism of claim 8, wherein the bypassswitch has circuitry that comprises: a positive bypass switching MOSFET;and a negative bypass switching MOSFET.
 12. The mechanism of claim 9,further comprising a MOSFET gate signal shaper that provides a gatesignal to the power steal module that softens a transition of turning onor off of the one or more MOSFETs.
 13. The mechanism of claim 8, furthercomprising: an SCR control signal circuit having an output that providesthe control signal to the input of the SCR circuit; and wherein thecontrol signal provided to the input of the SCR circuit results inmaking power available or not available at the second connection of theSCR circuit.
 14. The mechanism of claim 13, wherein: the secondconnection of the SCR circuit is connected to the load; and the load isa heater.
 15. A power supply unit for a thermostat and electric heatercomprising: a bypass switch circuit having an input connectable to afirst line voltage; a power steal device having an input connectable toan output of the bypass switch circuit; an energy storage having aninput connected to an output of the power steal device; an SCR gatesignal circuit having an input connected to an output of the energystorage; and an SCR circuit having an input from an output of the SCRgate signal circuit and an input connectable to a second line voltage,and having an output for providing a controlled second line voltage. 16.The unit of claim 15, wherein the bypass switch circuit comprises one ormore MOSFET switches.
 17. The unit of claim 16, further comprising alinear regulator connected to the output of the energy storage.
 18. Theunit of claim 15, further comprising a zero crossing detector having aninput connectable to the second line voltage.
 19. The unit of claim 18,further comprising a FET gate signal shaping circuit having an input forreceiving zero crossing information from the zero crossing detector andhaving an output for providing a sync signal to the bypass switchcircuit.
 20. The unit of claim 19, further comprising a reverse waveprotection circuit having an input connected to the first line voltage,a second input connected to the output of the energy storage, and havingan output for providing a protect signal to the FET gate signal shapingcircuit.
 21. The unit of claim 16, wherein the power steal devicecomprises one or more MOSFET switches.